This task order is for a phase 0 trial using linaclotide, a novel guanylyl cyclase C (GCC) agonist for colorectal cancer prevention. The trial will study 12 - 18 healthy adult volunteers who will be treated for 7 days and will undergo pre-and post-treatment colonoscopies with multiple biopsies at different sites within the large intestine to determine the biological effect of a once daily dose of linaclotide on cGMP expression, looking for a 60% inhibition. Initially 12 subjects will be treated (6 placebo and 6 with active agent). If insufficient activity is found in colorectal biopsies, an additional cohort of 6 subjects wil be treated with a hight dose of linaclotide. Multople secondary endpoints will also be assessed and activity will be assessed along 3 different sites in the large intestine.